1. Field of the Invention (Technical Field)
The present invention relates to a medical device with a hydrophilic and lubricious coating, wherein a hydrophilic polymeric unit is cross-linked by means of a plasma process with a double bond monomer, wherein the coating optionally further includes a bifunctional spacer to which the hydrophilic polymeric unit is bound.
2. Background Art
Note that the following discussion refers to a number of publications by author(s) and year of publication, and that due to recent publication dates certain publications are not to be considered as prior art vis-a-vis the present invention. Discussion of such publications herein is given for more complete background and is not to be construed as an admission that such publications are prior art for patentability determination purposes.
For many medical devices, it is preferable if a coating or other contacting surface has several properties, including biocompatibility and lubricity. Device surfaces and coatings that are water absorbent and lubricious may be effectively employed with, for example, stents, screws, tubing, catheters, wire guides, needles, sutures, and the like. Coatings that are hydrophilic and lubricious can be contacted with tissues with decreased trauma. For example, any medical device, such as a bandage, suture, tubing, catheter, guide wire and the like, may be more conveniently removed with less trauma to associated tissue if the surface is lubricious.
Similarly, it is a requirement for medical device surfaces that the surface or other coating be biocompatible. Any implantable medical device requires biocompatibility, in order to avoid adverse reactions. In normal application, such devices are expected to function in intimate contact with living tissue and blood. This contact requires a delicate balance between ensuring that the device can function in the complex extra- and intra-cellular environment and maintaining the living tissues and blood.
Lubricity is, in part, related to biocompatibility and thromboresistance, particularly since the degree of lubricity of a coating is related to wear of the coating due to contact with other surfaces. For devices, such as needles, sutures, catheters and the like, that transit tissue or abrasive substrates, a high degree of lubricity is desired, concomitant with biocompatibility and a high degree of wear resistance. Thus coatings that are lubricious, but are not resistant to contact with tissue or abrasive substrates, do not function well in medical devices.
Long-term use of most polymeric substrates frequently results in mechanical failure, the promotion of blood clot formation, or physical degradation due to unfavorable interactions with tissue or blood environments. Thus it is desirable to have coatings or other composites for polymeric substrates that are hydrophilic and lubricious, provide superior strength, do not promote blood clot formation, and which do not interact with the tissue or blood environment. The specific requirements of each device vary depending on the degree and duration of contact and the nature of the application.
Cross-linking of polymers to form a lubricious surface has been explored. For example, International Patent Application WO 02/053664, entitled Absorbent, Lubricious Coating and Articles Coated Therewith, discloses a coating consisting of a cross-linked hydrogel copolymer including water soluble base polymers with graft polymerized organic moieties that react with water to form a silanol group, wherein the copolymer is cross-linked through the silanol groups. However, in this coating and method the crosslinking is solely through the silane groups, forming an Si—O—Si cross-link. U.S. Patent Application No. 2002/0049281, Process for Cross-Linking Hyaluronic Acid to Polymers, discloses a method for double crosslinking of hyaluronic acid derivatives, presumably with one bond formed by cross-linking via hydroxyl groups and the other via, for example, carboxyl groups. However, this method requires lengthy reactions, up to forty-eight hours, and extreme pH changes, ranging from less than pH 4 to pH 12. U.S. Pat. No. 6,169,127, entitled Plasma-Induced Polymer Coatings, discloses coatings for contact lenses utilizing after-glow plasma-induced polymerization of an unsaturated monomeric compound, with cross-linking by concurrent after-glow plasma-induced polymerization of two monomers, such as a primary monomeric vinyl compound and a cross-linking agent. This method requires co-polymerization of the two monomers, and does not permit prior application of a monomer or polymeric unit to be subsequently cross-linked or chemical complexation of a monomer or polymeric unit to a linking moiety with the crosslinking subsequent to such complexation.
Prior art coatings employing plasma polymerization are known in the art. These include the coatings and methods disclosed in U.S. Pat. No. 5,463,010, to Hu, et al., entitled Hydrocyclosiloxane Membrane Prepared By Plasma Polymerization Process; and U.S. Pat. No. 5,650,234, to Dolence et al., entitled Electrophilic Polyethylene Oxides for the Modification of Polysaccharides, Polypeptides (Proteins) and Surfaces. However, these methods do not disclose plasma crosslinking utilizing a polymerizable hydrophilic polymeric unit in conjunction with a plasma consisting of a double bond monomer.
None of the preceding references disclose coatings or methods wherein base hydrophilic polymeric units applied by conventional means, such as dipping, are subsequently cross-linked by plasma polymerization of a monomer, such as a double bond monomer, resulting in a hydrophilic and lubricious coating.